As a junior in high school, I read the biography Edie: An American Life by Jean Stein and George Plimpton, so I knew she grew up on a ranch, the troubled scion of a privileged family, had been institutionalized at Silver Hill and sculpted a horse at Radcliffe. In 1965, she became the most glamorous of Warhol’s “superstars,” the one who best set off his own spectral image when they appeared in photographs together.